During the coming year studies will be performed to determine whether the dilatation called sustained dilatation, which can be elicited by stimulation of the lumbar sympathetic nerves in the dog pretreated with agents which prevent release of or deplete adrenergic amines, is brought about by formation of a false transmitter in adrenergic vesicles from which it is released during stimulation of the nerves. For this purpose a study will be performed to determine whether dopamine-beta-hydroxylase is released under conditions conducive to the elicitation of sustained dilation. Other studies will be undertaken in an effort to elucidate the nature of the substance responsible for peripheral inhibition of adrenergic discharge. Companion studies will be carried out to determine whether the peripheral inhibition is in reality an artifact resulting from a shift in the ratio of alpha to beta receptor activation. Helically cut arterial strips will be used as a screening procedure to test for the presence of dilator nerves distributed to blood vessels of various vascular beds throughout the body. Control studies will be performed by performing denervation of various vascular beds several days before removal of the blood vessels from which the helical strips will be prepared. Further attempts will be made to dissociate release of histamine from interstitial spaces and hypothetical peripheral pools responsible for the active component of reflex dilatation which occurs when reflexogenic agents are administered to the dog. For this purpose the gracilis muscle preparation will be used and will be prelabeled with radiolabeled histamine and other appropriate markers.